Resumo:
In this work, the effects of metal inert gas (MIG) welding on the microstructure and mechanical properties of a UNS S41003 steel were studied. UNS S41003 steel sheets were welded with AISI 309LSi wire using two different welding energies (high energy – HE and low energy – LE). Samples extracted from the base metal (BM), heat affected zone (HAZ) and fused zone (FZ) were subjected to microhardness and Charpy impact tests. Tensile tests were performed on samples extracted from the BM. Micrographic analyzes of the structures obtained in the welds were performed using scanning electron microscopy (SEM). Microfractographic images of tensile and impact fractures were obtained by scanning electron microscopy (SEM). As a result, the predominance of austenitic microstructure with the presence of delta ferrite islands was observed in the FZ. In HAZ there was a pronounced increase in the grain size of the ferrite phase with the existence of martensite needles predominantly in its grain boundary. The BM showed greater hardness than the metal from the FZ and HAZ. The impact energy was higher in the FZ compared to BM and HAZ.
